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Relevance: GS Paper III — Internal Security, Defence Technology, Indigenisation Source: MoD / ANI defence sources, June 2026

Fourth S-400 ‘Sudarshan’ Squadron Arrives: India’s Air Defence Grid Thickens

1 · What happened

India has received the fourth squadron of the Russian S-400 Triumf air defence system — known in Indian Air Force (IAF) service as “Sudarshan”. It will soon be deployed on an operational sector, likely along the western front.

  • The induction is part of the 2018 contract worth $5.43 billion (≈ ₹35,000 crore) for five squadrons. Three were inducted earlier; the fifth is expected by late 2026 / 2027. Deliveries were delayed by the Russia-Ukraine war. The S-400 saw combat validation during Operation Sindoor (May 2025).
  • India is also integrating indigenous AI-based decision support with the system (final firing decision stays with the human operator). The Defence Acquisition Council (DAC) has also cleared procurement of five additional S-400 squadrons.

2 · How India’s Air Defence Grid is built

Layered Air Defence (AD): No single weapon can stop every threat. India uses overlapping outer–middle–inner shields so that a missile slipping past one layer is intercepted by the next. The S-400 sits at the outermost layer.

Outer Shield (Imported)
S-400 Triumf “Sudarshan”
Range up to 400 km, altitude ~30 km. Engages fighters, cruise missiles and tactical ballistic missiles. Four squadrons now in country.
Indigenous Way Forward
Project Kusha + Mission Sudarshan Chakra
Project Kusha (ERADS) — DRDO’s S-400 rival, due 2028–30, with M1/M2/M3 interceptors up to ~400 km. Sudarshan Chakra (target 2035) will network all AD systems.
Inner Mechanism
Middle & short-range layers
MRSAM / Barak-8 (Indo-Israeli, medium range) plus Akash and Spyder for point defence of vital strategic assets.
The Risk Frontier
Hypersonics + supply shocks
Hypersonic glide vehicles (HGVs) at >Mach 5 evade conventional radars. Wars (Ukraine) expose foreign-supply vulnerability; multi-vendor integration creates digital blind spots.

  • DRDO’s BMD Programme: Two-tier shield — PAD (Prithvi Air Defence) for exo-atmospheric kills (50–80 km), AAD (Advanced Air Defence) for endo-atmospheric kills (15–30 km).
  • S-500 (Prometheus): Russia’s next-gen system — exo-atmospheric, ~600 km range; targets ICBMs, hypersonic glide vehicles and low-orbit satellites.
  • AI-in-the-loop: India’s integration of indigenous AI keeps the human operator as final decision-maker — aligned with global “meaningful human control” norms over lethal autonomous systems.

UPSC Value Box
S-400 Triumf (Sudarshan) Russian long-range mobile SAM system; range ~400 km; tracks up to 100 targets, engages dozens simultaneously. 2018 deal: $5.43 bn / ₹35,000 cr for 5 squadrons.
Project Kusha (ERADS) DRDO’s Extended Range Air Defence System; three interceptors M1 (150 km), M2 (250 km), M3 (350–400 km); induction window 2028–30.
BMD Programme: PAD & AAD DRDO’s two-tier ballistic-missile shield. PAD = exo-atmospheric (above ~50 km). AAD = endo-atmospheric (below ~30 km). Easy memory: PAD = Plus (higher), AAD = Atmosphere (within).
Mission Sudarshan Chakra (2035) Networked multi-domain AD architecture to interlink Russian, Israeli and Indian systems; uses AI, quantum computing, large language models against swarm drones & hypersonics.
S-500 Prometheus Russian next-gen exo-atmospheric / near-space defence; ~600 km range, hit-to-kill capability against ICBMs, HGVs, low-orbit satellites.
Operation Sindoor (May 2025) First combat use of S-400 by India; cited by officials as a successful demonstration against aerial threats from Pakistan.
Defence Acquisition Council (DAC) Apex Ministry of Defence body chaired by the Raksha Mantri; approves all major capital acquisitions for the armed forces.

MCQ Practice Question
Q. With reference to India’s air defence systems, consider the following statements:

  1. The S-400 Triumf, inducted in Indian Air Force service as “Sudarshan”, was procured under a 2018 contract with Russia for five squadrons.
  2. Under DRDO’s Ballistic Missile Defence Programme, the Advanced Air Defence (AAD) missile is designed for exo-atmospheric interception, while the Prithvi Air Defence (PAD) missile handles endo-atmospheric interception.
  3. Project Kusha is an indigenous long-range air defence system being developed by DRDO with interceptors of varying ranges, comparable in coverage to the S-400.

Which of the statements given above is/are correct?
(a) 1 and 2 only    (b) 2 and 3 only    (c) 1 and 3 only    (d) 1, 2 and 3

Answer: (c) 1 and 3 only

  • Statement 1 — Correct: The IAF designation for the S-400 is “Sudarshan”. The $5.43 bn deal signed in 2018 covers five squadrons; the fourth has just arrived (June 2026).
  • Statement 2 — Incorrect (the trap): The roles are swapped. PAD = exo-atmospheric (high altitude, 50–80 km, intercepts before re-entry). AAD = endo-atmospheric (low altitude, 15–30 km, the inner backup tier). Aspirants often confuse the two because both names use “Advanced/Prithvi” — remember PAD goes higher.
  • Statement 3 — Correct: Project Kusha (ERADS) is DRDO’s indigenous extended-range AD system with three interceptors — M1, M2 and M3 — reaching up to ~400 km, putting it in the same operational class as the S-400.

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